over reving series92 ?

Low Class · June 07, 2012, 04:08:42 PM

Just curious. 2200 or so, seems to be the max reccomended rpm for a long lived engine. The military and some of the (rich) boat people turn them quite a bit higher and rebuild in as little as 1000 hours, I have read.

My question is: what all fails? Rod or main bearings? Pistons? Rods? What else?

Zeroclearance · June 07, 2012, 04:16:44 PM

Rod>> I have the rod to prove it.

luvrbus · June 07, 2012, 06:32:52 PM

Most boat people using the 750 hp 8v92 turn the engines to 2500 max for a short burst and cruise at 1800 to 1900 rpm 90% of the time a steady diet of 2500 rpms on a 92 series will blow the tips on the injectors above that you are in no mans land lol.

The miltary does turn the 8v71 up to 2500 and the 53 series I have saw those set 3000 to 3200 rpm in some of the Navy's boats but never saw a military 8v92 set above 2200

Geoff · June 07, 2012, 06:39:45 PM

You wear out the top end of the engine running oversize injectors at 2300-2500 rpms. Plus all the bearings take a beating. Like you said-- the engine won't last.

Len Silva · June 08, 2012, 06:00:13 AM

I have heard it said that the most reliable predictor of engine life is the amount of fuel consumed. That is, a particular engine will last for X gallons or pounds of fuel, no matter how hard or easy you work it. Makes sense to me.

chev49 · June 08, 2012, 07:33:48 AM

one would then think that the fulie dragster engines would last more than 1000'...

HB of CJ · June 08, 2012, 04:07:42 PM

Ancient history, but important to us Bus Conversion people still running the old DD 2 strokes. The 71 series may have been the tougher engine. The 92 series stressed the rods in particular, as well as the heat problem in the heads inherent trying to squeeze more HP (and heat) out of an established design. Amazing platform.

Way back in the day, we were lectured and threatened with a fate worserer than death by the master fire mechanic if we over revved the new 92 DD in the newer Fire Apparatus. 2100 max cruising and no more than 2300 rowing thru the manual tranny gears. Oh boy, were those the days. He he he. HB of CJ (old coot)

Geoff · June 08, 2012, 05:26:06 PM

Quote from: HB of CJ on June 08, 2012, 04:07:42 PM
Ancient history, but important to us Bus Conversion people still running the old DD 2 strokes. The 71 series may have been the tougher engine. The 92 series stressed the rods in particular, as well as the heat problem in the heads inherent trying to squeeze more HP (and heat) out of an established design. Amazing platform.

Way back in the day, we were lectured and threatened with a fate worserer than death by the master fire mechanic if we over revved the new 92 DD in the newer Fire Apparatus. 2100 max cruising and no more than 2300 rowing thru the manual tranny gears. Oh boy, were those the days. He he he. HB of CJ (old coot)

Ancient history revisited-- When DD cam out with the 92 series they had problems, that is why there is s Silver 92 with improved cooling in the heads to take care of the earlier problems.

TomC · June 09, 2012, 08:06:40 AM

The 92 series is definitely a slower running engine then the 71 series. I would set the no load on a 92 series no higher then 2300rpm. On a 71 series 2500rpm is not a problem. In the 70's there were truck drivers that had 71 series turned up to 2800rpm without much problems. My 8V-71TATAIC is set at 2500rpm-although I don't go much over 2100rpm since it just uses more fuel. Good Luck, TomC